A. Field of the Invention
The present invention relates generally to the communications field, and, more particularly to a fiber optic cable stripping and measuring assembly, and a method for stripping and measuring a fiber optic cable using the same.
B. Description of the Related Art
Along with the increasing prominence of the Internet has come the wide-ranging demand for increased communications capabilities, including more channels and greater bandwidth per channel. Optical media, such as fiber optic cables, promise an economical alternative to electrical conductors for high-bandwidth long-distance communications. As described in U.S. Pat. No. 6,079,297, assigned to the assignee of the present application, a typical fiber optic cable consists of a silica glass core region that provides a path for optical signals traveling along the cable. The core region is surrounded by a cladding region whose refractive index may be altered to achieve a desired propagation path of the optical signals traveling along the core region. The cladding region is in turn surrounded by an outer protective coating to protect the core region and the cladding region from damage, such as nicks, scratches or dents, which could degrade the long term quality and performance of the fiber optic cable. A fiber optic cable is also protected by a buffer layer that is typically a firm polymer which provides increased protection to the fiber while also increasing the fiber bending stiffness. The buffer layer is formed directly around the protective coating and there is usually a significant adhesive force between the buffer layer and the protective coating.
The glass optical fibers of fiber optic cables have very small diameters, which are susceptible to external influences such as mechanical stress and environmental conditions. The index of refraction of the core is higher than the index of refraction of the cladding to promote internal reflection of light propagating down the core.
Certain uses of fiber optic cables require that a portion of the buffer layer be removed from the fiber optic cable. For example, to make a fiber optic coupler, the buffer layers are stripped from portions of at least two fiber optic cables, and the stripped portions are fused (spliced) together in side-by-side relationship and stretched. It is important that the stripped portions of the fiber optic cables do not become weakened during the stripping process since weakened fiber optic cables can fail during subsequent process steps or during handling of the coupler when tensile stress is applied to the exposed glass optical fiber.
A buffer layer of a fiber optic cable may be removed or stripped in a variety of ways. Buffer layers can be mechanically stripped from an optical fiber by placing the fiber within a precision linear stripper as disclosed in U.S. Pat. No. 6,079,297, discussed above, bringing blades of the stripper into contact with opposite sides of the buffer layer, and then moving the tool relative to the axis of the buffer layer. The bare portion of the fiber usually needs to be wiped with a cloth wetted with alcohol or the like to remove smudges and/or particles of buffer layer that have been deposited on the bare portion of optical fiber by the buffer layer removal process. This type of buffer layer removal process has been built into equipment that performs the tasks of the technician, whereby the process may no be longer manual.
Fiber optic cables are prepared prior to splicing to another fiber optic cable, or joining to a terminating device, by cleaving the fiber to obtain a high-quality endface. In order to obtain low optical losses, the endface of the fiber must be substantially flat and without flaws. In addition to endface quality, one parameter of importance is the angle of the endface to the optical axis of the optical fiber. It is desirable that the plane of the endface be normal to the optical axis, with the fracture angle measuring deviation from the normal.
When the fiber optic cables of two optical components are to be joined or spliced, the end portions of the buffer layers of the fiber optic cables need to be removed. The end portions of the fiber optic cables also need to be cleaved to form endfaces. Typically, the endfaces are formed a predetermined distance from the optical components, by measuring the predetermined distance from the optical component. The endfaces of the cables may then be fusion spliced together. As used herein, the term xe2x80x9csplicexe2x80x9d refers to the assembly of a fused joint of fiber optic cables, and, generally, although not necessarily, a reinforcing bar and a protective sheath (also known as a splice protector).
The optical components may then be installed in an optical communications circuit. Typically, the fused fiber optic cables joining the two optical components are routed, bent, and/or stored in the optical communications circuit. The joined fiber optic cables may be wrapped around two storage mandrels, providing straight and bent portions of the joined fiber optic cables. Therefore, the splice joining the two cables is preferably formed at a portion of the cables that is not bent when they are routed, bent, or stored in the circuit. That is, the splice is preferably formed at straight portions of the joined fiber optic cables. When the splice of the joined fiber optic cables is located a straight portion, the splice is subjected to less mechanical stresses than would occur if it were formed at a bent portion.
Since there is typically excess fiber optic cable when the two optical components are spliced, the predetermined distance for forming the endfaces of the cables may occur at multiple points along the lengths of the fiber optic cables. This is fortunate since the cleaving and splicing of fiber optic cables is not always successful.
When the cleaving or splicing of fiber optic cables is unsuccessful, additional lengths of the fiber optic cable buffer layer may need to be removed, and predetermined distances from the optical components for the locations of the endfaces must be measured. The new predetermined distances preferably will occur at a portion of the cables that is not bent when they are routed, bent, or stored in the circuit. Currently, the measurement of the predetermined distances is manually performed by measuring, with a ruler, the distance from the optical components to the desired location of the endfaces. This measurement is cumbersome and time consuming.
Thus, there is a need in the art to easily strip the outer buffer layer of a fiber optic cable and measure predetermined points on the fiber optic cable that may be used as splice points.
The present invention solves the problems of the related art by providing an apparatus that strips the outer buffer layer of a fiber optic cable, and measures predetermined splice points on the stripped portion of the cable. The apparatus of the present invention may be used in a method for stripping and measuring a fiber optic cable.
In accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises a fiber optic cable stripping and measuring apparatus, comprising: a fiber clamp for securing a first portion of the fiber optic cable; a fiber stripper spaced from said fiber clamp for scoring a buffer layer of the fiber optic cable to enable the buffer layer of a portion of the fiber optic cable to be removed to expose an optical fiber within the fiber optic cable; and a marking mandrel spaced from said fiber stripper and having a circumference that exceeds the minimum bend radius of the fiber optic cable, said cylindrical marking mandrel having a marking groove formed on its periphery so that the exposed optical fiber of the fiber optic cable may be marked at a predetermined location.
Further in accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises a method for stripping and measuring a fiber optic cable with an apparatus having a fiber clamp, a marking mandrel having a circumference that exceeds the minimum bend radius of the fiber optic cable, and a fiber stripper interposed between and spaced from the fiber clamp and the marking mandrel, comprising: securing a first portion of the fiber optic cable with the fiber clamp; scoring a buffer layer of the fiber optic cable with the fiber stripper; removing a portion of the buffer layer of the fiber optic cable to expose an optical fiber within the fiber optic cable; wrapping the exposed optical fiber around the marking mandrel; and marking a predetermined location of the exposed optical fiber using a marking groove formed on the periphery of the marking mandrel.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.